Hello nbszroro
I am sorry, you didn't understand my solution and it's right. Review it .( I changed the i=0,50 instead i=1,50, I missed the 0, sorry). It does not fail for neither case (remember 0!=1).
Sumatory of 100!/((2i!)*(100-2i)!), where i=0,50.
Regards
Question: A stair of 100...